FIG. 1 illustrates a prior art signal-processing device 10, in the example shown a sound signal amplifier as a main distortion generator in the circuit. The input 12 accepts a signal, for example a line level signal, from an audio source such as a CD player, musical DAC device or the like. The device 10 amplifies the input signal and via output 14 transmits the amplified signal to a transducer, for example conventional electromagnetically-driven speaker, to generate sound waves corresponding to the output electrical signal.
The processing of any electrical signal, for example modulation-demodulation, analog-to-digital (ADC) and digital-to-analog (DAC) conversions or amplification as in the embodiment illustrated, can distort the signal waveform. According to Fourier's theorem, the damaged original sine signal (as with every periodical signal) can be represented as the sum of sine signals of divisible frequencies (harmonics), the lowest harmonic frequency (1st harmonic) being the fundamental frequency of the original signal. A coefficient of divisibility provides the number of each harmonic. Under the principle of superposition, all harmonics above the fundamental are additive to the original signal sine waveform and therefore cause signal distortion. Thus, in order to restore the original signal waveform, it is sufficient to suppress all harmonics except the 1st harmonic (fundamental).
If the original signal has a sine form of stable frequency, the distorted signal can typically be corrected by a high-quality resonance pass filter having the same frequency as the original elementary signal. Such a filter will pass only the original signal frequency, and thus eliminate higher harmonics to restore the original signal waveform. However, when the original signal contains two or more elementary (sine) signals of random frequencies, this method cannot be used to restore the original signal waveform from a processed signal.
It would accordingly be beneficial to provide a system and method for the reduction of signal distortion in a processed signal consisting of multiple frequency sine components.